Remote UE Cell Change Handling for Sidelink Relay Path Switching
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Solution Overview
Problem
During indirect path switching in communication systems, particularly when a relay UE is in RRC_IDLE/INACTIVE state, changes in the serving or camping cell of the relay UE can lead to failures in handover procedures due to incorrect cell identification, causing path switching failures.
Innovation Solution
The remote UE detects changes in the serving or camping cell of the candidate relay UE by receiving updated messages and initiates an updated measurement report or radio resource control connection re-establishment procedure to ensure accurate path switching decisions, even if the relay UE has reselected to a different cell during the path switching preparation phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the relay UE is in RRC_IDLE/INACTIVE state during indirect path switching, then the relay UE can perform cell reselection to optimize coverage, but the serving cell change causes handover procedure failures due to incorrect cell identification
Solution Approach 1:
The remote UE performs preliminary detection of the relay UE's current serving cell by receiving system information or discovery messages before finalizing the path switching decision. This preliminary action allows the remote UE to identify mismatches between the reported and actual serving cells, enabling corrective measures before handover failure occurs.
Solution Approach 2:
The system implements feedback mechanisms where the relay UE periodically reports its current serving cell status, and the remote UE sends measurement reports containing detected cell information to the network node. This feedback loop enables continuous monitoring and correction of cell identification errors during path switching.
2Stability of the object's composition
If the relay UE changes serving cell during path switching preparation, then the relay UE can maintain optimal connection, but the path switching fails due to incorrect cell identification in measurement reports
Solution Approach 1:
The measurement report mechanism provides feedback from the remote UE to the network node about the relay UE's actual serving cell status. This feedback enables the network to detect identification errors and correct path switching decisions accordingly.
Solution Approach 2:
The remote UE performs preliminary verification of the relay UE's serving cell status by receiving and processing system information or discovery messages before committing to the path switching procedure, preventing incorrect cell identification from causing failures.
3Reliability
If the remote UE sends updated measurement reports frequently to track relay UE cell changes, then path switching reliability improves, but the signaling overhead and processing complexity increase
Solution Approach 1:
Instead of continuous monitoring, the system uses periodic measurement reports triggered by specific events such as detecting a serving cell change or receiving system information updates. This periodic approach maintains reliability while reducing unnecessary signaling overhead.
Solution Approach 2:
The feedback mechanism is event-driven rather than continuous, activating only when significant changes occur in the relay UE's cell status. This selective feedback approach balances reliability requirements with signaling overhead management.
Data Source
AI summary
In an example embodiments, sending, by a remote user equipment (UE) of a source cell, towards a network node of the source cell a measurement report including a candidate relay (CR) list, wherein the CR list includes at least a cell identification for at least one CR UE for an indirect path switching from the source cell to a target cell associated with a CR UE; detecting a change of a serving cell or camping cell of the CR UE from the target cell to another cell based on receiving from the CR UE at least one message that indicates at least one cell identification for the CR UE is different than reported; and based on the detecting, sending an updated measurement report towards the network node triggering renewing a path switch decision or initiating a radio resource control connection re-establishment procedure with the source cell or the target cell.